1G9Y: Homing Endonuclease I-Crei Dna Substrate Complex With Calc
reference: The homing endonuclease I-CreI uses three metals, one of which is shared between the two active sites., Chevalier BS, Monnat RJ Jr, Stoddard BL, Nat Struct Biol 2001 Apr;8(4):312-6. PMID: 11276249

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).